Interlock and forced air furnace and HRV

Abstract

An electrical interlock ties a heat recover ventilator to circulation air blower operation of an associated forced-air furnace or air conditioning system. This ensure that the blower circulates supply and return air within the building or dwelling. An interlock relay has its coil energized by the heat recovery ventilator, and a normally open contact tied to the control of a blower of the forced-air system. The furnace or air conditioner and the ventilator are operated by separate controls located within the building's comfort space. When the ventilator is operated, the circulation blower runs continuously, but thermostat actuate of the furnace or air conditioner above will not operate the ventilator.

What is claimed is: 
     
       1. A forced air comfort system in which a circulation air blower is actuated in response to a thermostat control signal from a thermostat in an indoor comfort space and circulates indoor air from the comfort space through a supply duct to a heat exchanger which treats the indoor circulation air, and in which a supply duct returns the treated air from the heat exchanger to the comfort space; and comprising a heat recovery ventilator which discharges a portion of the circulation air to an outdoor environment and replaces the discharged circulation air with make-up air from the outdoor environment; the heat recovery ventilator including means to exchange heat between the discharged circulation air and the make-up air, blower means for inducing a flow of the make-up air from the outdoor environment and to induce a flow of the discharge air into the outdoor environment, and control means in the indoor comfort space electrically coupled to the blower means for electrically actuating same; and electrical interlock means coupling said furnace blower and the blower means of said heat recovery ventilator such that when the control means energize the blower means, the furnace blower is also energized to circulate said circulation air. 
     
     
       2. A forced air comfort system according to claim 1 wherein said interlock means includes a relay having an actuator coil electrically coupled to said blower means of said heat recovery ventilator, and contact means coupled to said circulation air blower. 
     
     
       3. A forced air comfort system according to claim 1 wherein said heat recovery ventilator has an indoor vent coupled to the return air duct and outdoor vents for discharging the discharge air outdoor and taking in the make-up air from outdoors. 
     
     
       4. A forced air comfort system according to claim 2 wherein said contact means includes a normally open contact coupled to said furnace blower, such that said furnace blower operates whenever said blower means of said heat recovery ventilator operates, but a call for actuation of the furnace blower without a call from said control means to actuate said heat recovery ventilator, will not operate said blower means. 
     
     
       5. A forced air comfort system according to claim 4, wherein said contact means further includes a normally closed contact disposed between said thermostat and a control for said furnace blower, such that actuation of said heat recovery ventilator opens said normally closed contact to isolate said thermostat from the control for said blower.